Integrated fluid sensing device

ABSTRACT

A circuit board, which includes one or more sensors, is integrated in a fluid control device, such as a valve manifold and a base plate. The fluid control device selectively directs a fluid used to control pneumatic or hydraulic equipment. The sensors are used to measure physical characteristics of the fluid, such as flow rate, pressure, and temperature. A flow sensor includes a paddle and a support member. The paddle is disposed at least partially in an orifice and is displaced in response to fluid flow. The support member positions the paddle in the orifice and includes a plurality of strain gauges. The strain gauges are disposed on only one side of the support member and are mechanically stressed in response to the paddle being displaced by the fluid flow.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 09/666,990 filed Sep. 21, 2000, the disclosure ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to pneumatic and hydraulicequipment, and more particularly to the measurement of physicalcharacteristics, such as flow rate, pressure, and temperature of a fluidused to control these devices.

[0004] 2. Description of the Prior Art

[0005] A fluid flow device, such as a valve manifold 10 and itscorresponding base plate 12 shown in FIG. 1, is used to accuratelydirect fluids used to control pneumatic and/or hydraulic equipment.Fluid flow devices and other control devices are disclosed in U.S. Pat.Nos. 5,348,047 to Stoll, et al. and 5,458,048 to Hohner, which areincorporated herein by reference. The term “fluid” is generically usedherein to refer to any gas, liquid, suspension, and/or slurry used as acontrol medium in such equipment.

[0006] The base plate 12 is mounted to a bottom surface of the valvemanifold 10, as shown by dashed lines in FIG. 1. The base plate 12includes channels 16, which pass through the base plate 12 and coincidewith apertures on the underside of the fluid flow device 10. A fitting14 is fitted to one end of each of the channels 16. The fittings 14 canreadily be connected to tubes that direct the fluid to and/or from thevalve manifold 10. The channels 16 then direct the fluid through thebase plate 12 to the appropriate aperture in the valve manifold 10. Thevalve manifold 10 can then redirect or modify the flow of fluid inresponse to electronic control. In addition to directing the flow offluid, another function that may be performed is the measurement offluid characteristics, such as flow rate, pressure, and temperature.

[0007] To incorporate the flow sensor shown in FIGS. 2a, 2 b, and 2 c inconventional fluid flow devices, additional tubing, fittings, andconnectors must be spliced into the network of tubes coupling the baseplate 12 to and from the source of the fluid and portions of theequipment to be controlled. The additional tubes, fittings, andconnectors increase measurement error, space requirements, and the costof installing and maintaining the equipment. In addition, theelectronics that monitor the sensors require a substantial amount ofadditional wiring, which adds to the clutter of the resulting system andseverely degrades its reliability. Further, the sensors and associatedelectronics, by being externally located to the fluid flow device, areinherently unprotected from environmental hazards, such as shock, dust,and pollutants, which are common in and around hydraulic and/orpneumatic equipment.

[0008] U.S. Pat. No. 3,424,000 to Chelner et al. (Chelner) describes aflow sensor, which includes four (4) strain gauges mounted on both thefront and rear sides of a wafer. The wafer is deflected in response tofluid flow and provides a substrate for mounting strain gauges,electrical conductors, and contacts.

[0009] However, to modify the sensitivity of the Chelner flow sensor,the substrate for the electrical components must be modified, which hasa significant impact on the deposition of electrical components thereon,and thus the overall manufacturing and standardization process. Inaddition, the double-sided placement of strain gauges on the wafersubstantially complicates and adds to the cost of passivation andproduction of such flow sensors.

OBJECTS AND SUMMARY OF THE INVENTION

[0010] It is an object of the present invention to provide an integratedfluid sensing device, which significantly reduces measurement errors,space requirements, and the cost of installing and maintaining sensorsthat measure the physical characteristics of a fluid used to controlhydraulic or pneumatic equipment.

[0011] It is a further object of the present invention to provide anintegrated fluid sensing device, which includes sensors mounted on asingle circuit board having common signal processing, communication,error control, and connecting circuitry.

[0012] It is still a further object of the present invention to providean integrated fluid sensing device, which can readily be adapted tovarious physical characteristics of a fluid used to control hydraulic orpneumatic equipment by changing a single circuit board.

[0013] It is yet a further object of the present invention to provide anintegrated fluid sensing device, which can readily display and transmitsensed data, via wired or wireless means, which represents physicalcharacteristics of a fluid used to control hydraulic or pneumaticequipment.

[0014] It is still another object of the present invention to provide anintegrated fluid sensing device that significantly reduces the amount ofexternal tubing, connectors, and fittings required to sense the physicalcharacteristics of a fluid used in the control of hydraulic or pneumaticequipment.

[0015] It is yet another object of the present invention to provide anintegrated fluid sensing device, which substantially encloses sensorsthat measure the physical characteristics of a fluid and protects thesesensors against environmental hazards.

[0016] It is another object of the present invention to provide a flowsensor, which can readily be adapted to different flow rates without anysubstantial change or additional cost in the manufacturing process.

[0017] It is yet another object of the present invention to provide aflow sensor, in which a generic support member includes one or morestrain gauges.

[0018] It is still another object of the present invention to provide aflow sensor, in which a paddle that is displaced by fluid flow does notinclude a strain gauge.

[0019] It is a further object of the present invention to provide a flowsensor, in which a support member includes strain gauges on only oneside of the of the support member.

[0020] In accordance with the present invention, an integrated fluidsensing device is provided, which includes a fluid flow device and acircuit board. The fluid flow device includes a first mating portion anda second mating portion. The first mating portion includes a firstaperture, and the second mating portion includes a second aperture. Thefirst aperture and the second aperture are at least partially alignedsuch that the first aperture and the second aperture define a firstchannel through the first and second mating portions when the first andsecond mating portions are joined together. The first channel is able tocommunicate fluid therethrough. The circuit board is disposed betweenthe first mating portion and the second mating portion and includes atleast one sensor. The sensor is at least partially aligned with thefirst channel and is able to detect a physical characteristic of thefluid flowing through the first channel.

[0021] In further accordance with the present invention, a method ofintegrating a sensor in a fluid flow device is provided, which includesthe steps of dividing the fluid flow device into a first mating portionand a second mating portion, and positioning a circuit board between thefirst mating portion and the second mating portion. The first matingportion including a first aperture, and the second mating portionincluding a second aperture. The first aperture and the second apertureare at least partially aligned such that the first aperture and thesecond aperture define a first channel through the first and secondportions when the first and second mating portions are joined together.The first channel is able to communicate a fluid therethrough. Thecircuit board includes at least one sensor, which is at least partiallyaligned with the first channel. The sensor is able to detect a physicalcharacteristic of the fluid flowing through the first channel.

[0022] In still further accordance with the present invention anintegrated fluid sensing device is provided, which includes at least onevalve, a base plate, and a circuit board. The base plate is removablycoupled to the valve and includes a first mating portion and a secondmating portion. The base plate includes a first channel through thefirst and second mating portions when the first and second matingportions are joined together. The circuit board is disposed between thefirst mating portion and the second mating portion. The circuit boardincludes at least one sensor and an electrical contact. The electricalcontact is coupled to the sensor and is accessible to an exterior of thefluid flow device when the first and second portions are joinedtogether. The sensor is at least partially aligned with the firstchannel and is able to detect a physical characteristic of the fluidflowing through the first channel.

[0023] In yet further accordance with the present invention, a flowsensor is provided, which includes a paddle and a support member. Thepaddle is disposed at least partially in an orifice and is displaced inresponse to fluid flow. The support member positions the paddle in theorifice and includes a plurality of strain gauges. The strain gauges aredisposed on only one side of the support member and are mechanicallystressed in response to the paddle being displaced by the fluid flow.

[0024] In accordance with the present invention, a method of sensingflow is provided, which includes the steps of disposing a paddle atleast partially in an orifice, directing a fluid flow through theorifice, positioning the paddle in the orifice by a support member, anddisposing the plurality of strain gauges on only one side of the supportmember. The paddle is displaced in response to the fluid flow. Thesupport member includes a plurality of strain gauges and the pluralityof strain gauges are mechanically stressed in response to the paddlebeing displaced by the fluid flow.

[0025] These and other objects, features, and advantages of the presentinvention will become apparent from the following detailed descriptionof illustrative embodiments thereof, which is to be read in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is an isometric view of a conventional fluid control deviceincluding a valve manifold and a base plate.

[0027]FIGS. 2a and 2 b are side views of a flow sensor.

[0028]FIG. 2c is an isometric view of the flow sensor shown in FIGS. 2aand 2 b.

[0029]FIG. 2d is an isometric view of a conventional hot-wireanemometer.

[0030]FIGS. 3a and 3 b are bottom and top views, respectively, of theconventional base plate shown in FIG. 1.

[0031]FIG. 3c is a side, cross-sectional view of the base plate shown inFIG. 3b taken along the line A-A′.

[0032]FIG. 4a is a side, cross-sectional view of the base plate in whicha circuit board has been inserted between an upper portion and a lowerportion of a base plate in accordance with the present invention.

[0033]FIG. 4b is a side, cross-sectional view of one channel in the baseplate shown in FIG. 4a.

[0034]FIG. 4c is a top, cross-sectional view of the base plate shown inFIG. 4b taken along the line Y-Y′.

[0035]FIG. 4d is a side, cross-sectional view of one channel in analternative embodiment of the base plate formed in accordance with thepresent invention.

[0036]FIGS. 4e and 4 f are top, cross-sectional views of two embodimentsof the base plate shown in FIG. 4d taken along the line X-X′.

[0037]FIG. 4g is a side, cross-sectional view of one channel in analternative embodiment of the base plate formed in accordance with thepresent invention without a bypass channel directing flow around thesensor.

[0038]FIGS. 5a and 5 b are partially-exploded, side, cross-sectionalviews of two embodiments of the base plate formed in accordance with thepresent invention.

[0039]FIG. 6a is a top view of a circuit board.

[0040]FIG. 6b is a side, cross-sectional view of the circuit board shownin FIG. 6a taken along the line B-B′.

[0041]FIG. 6c is an alternative embodiment of the circuit board shown inFIG. 6a, which includes an application-specific integrated circuit(ASIC).

[0042]FIG. 6d is an alternative embodiment of the circuit board shown inFIG. 6c, which includes a telemetric unit for wireless transmission ofsensor data.

[0043]FIG. 7a is a top view of a spacing layer.

[0044]FIG. 7b is a side, cross-sectional view of the spacing layer shownin FIG. 7a taken along the line C-C′.

[0045]FIG. 8a is a top view of a sealing layer.

[0046]FIG. 8b is a side, cross-sectional view of the sealing layer shownin FIG. 8a taken along the line D-D′.

[0047]FIG. 9 is a side, cross-sectional view of the integrated fluidsensing device formed in accordance with the present invention.

[0048]FIG. 10 is an isometric cross-sectional view of a flow sensorformed in accordance with the present invention.

[0049]FIG. 11 is an enlarged cross-sectional view of a portion of theflow sensor shown in FIG. 10.

[0050]FIG. 12 is a magnified view of an actual layout of a supportmember for the flow sensor formed in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] One type of sensor 18, which is used to measure the flow ofliquid, is shown in FIGS. 2a, 2 b, and 2 c. The flow sensor 18 includesan orifice 20, a cantilever paddle structure 22, and an implantedpiezo-resistive Wheatstone bridge 24. FIG. 2a shows the paddle structure22 in an undeflected state, and FIG. 2b shows the paddle structure 22 ina deflected state.

[0052] The fluid to be measured is directed through the orifice 20 inthe flow sensor 18. The dynamic pressure built up by the fluid deflectsthe paddle structure 22. The mechanical stress of the paddle structure22 changes the resistance of the piezo-resistive Wheatstone bridge 24 atthe base of the paddle structure 22, and this change in resistancecreates a corresponding change in voltage. The change in voltage isdetected on a set of contacts 26 electrically connected to theWheatstone bridge 24, as shown in FIG. 2c. For temperature compensation,a second Wheatstone bridge is preferably positioned on the flow sensor18 surrounding the orifice 20. A support member preferably positions thepaddle structure 22. The size of the support member is preferablyminimized to concentrate the mechanical stress of deflection, and thusincrease the sensitivity of the flow sensor 18. Furthermore, the overallsize of the flow sensor is determined by the paddle size, which can beadjusted to the specific needs of the control task.

[0053] The output voltage of the Wheatstone bridge 24 is proportional tothe square of the volumetric flow rate. The sensitivity of the flowsensor 18 is dependent upon the size of the orifice 20, and isadjustable over a broad range. Thus, since the paddle structure 22 isperpendicularly oriented to the direction of flow of liquid, as liquidpasses through the orifice 20 in the flow sensor 18, the kineticpressure of the liquid induces a mechanical stress that is detected bythe piezo-resistors in the Wheatstone bridge 24.

[0054]FIG. 3a shows a bottom view of a multipole or base plate 12.Threaded holes 28 are provided in the base plate 12 to accommodatefittings 14 as shown in FIG. 1. The fittings 14 enable tubes (not shown)to be connected to the base plate 12. The base plate 12 is preferablymanufactured as a separate unit from the valve 10 shown in FIG. 1 sothat the valve manifold 10 can be removed from the base plate 12 withoutdisturbing the tubes connected to the base plate 12.

[0055]FIG. 3b shows a top view of the conventional base plate 12including a line A-A′. FIG. 3c shows a side, cross-sectional view of thebase plate 12 taken across the line A-A′. The arrows K in FIG. 3cindicate the flow of fluid through the channel in the base plate 12. Asis best seen from FIG. 3C, the apertures in the top of the base plate 12are preferably offset from the corresponding apertures in the bottom ofthe base plate 12. This offset diverts the flow of fluid through thechannel, which limits the pressure of the fluid as it comes in contactwith components in the valve manifold 10.

[0056]FIG. 4a shows a side, cross-sectional view of the base plate 12after it has been separated into an upper portion 12A and a lowerportion 12B along a line X-X′ shown in FIG. 3c. A circuit board 30,which includes at least one sensor 18, is inserted between the upper andlower portions of the base plate. An arrow L indicates the flow of fluidthrough the channel and through the sensor 18. A bypass path L′ ispreferably provided to divert the majority of flow around the sensor 18.The bypass path L′ reduces the flow through the sensor 18, whichprotects sensitive components in the sensor 18 that are subject to wearand breakage. About 10-15% of the total flow of fluid is preferablyallowed to pass through the sensor 18. The remaining flow is divertedaround the sensor 18 and through the bypass path L′.

[0057]FIG. 4b shows a side, cross-sectional view of the base plateportions 12A, 12B and the circuit board 30 in which the bypass path L′has been implemented around the sensor 18. FIG. 4c is a top,cross-sectional view of the circuit board taken along cross-section lineY-Y′ showing an orifice 32 for the bypass path L′ and an orifice 34,which allows the flow of fluid through the sensor 18.

[0058]FIG. 4d shows an alternative geometry for the channel in the baseplate 12 having at least two (2) bypass paths L′. FIGS. 4f and 4 e showtop, cross-sectional views of the circuit board 30 taken alongcross-section line X-X′ shown in FIG. 4d. The circuit board 30 in FIG.4e accommodates six (6) bypass paths L′, and the circuit board 30 inFIG. 4f accommodates eight (8) bypass paths L′.

[0059] By appropriate dimensioning of the sensor 18, the channel may beconstructed without a bypass channel directing flow around the sensor18. FIG. 4g shows a side, cross-sectional view of the base plateportions 12A, 12B and the circuit board 30 in which a bypass path hasnot been implemented around the sensor 18. Thus, in the embodiment shownin FIG. 4g, about 100% of the flow is directed through the sensor 18.

[0060]FIG. 5A shows an alternative embodiment of the base plate, whichincorporates four (4) layers between the upper portion 12A and the lowerportion 12B of the base plate 12. An upper sealing layer 32A and a lowersealing layer 32B are preferably inserted above and below the circuitboard 30, respectively. The sealing layers are preferably manufacturedfrom a pliable and/or deformable material, such as rubber, whichsubstantially prevents leakage of the fluid from the channel. Leakage isparticularly prevalent between the hard surfaces of the circuit board 30and the base plate 12A. In addition, a spacing layer 34 is preferablyinserted above or below the circuit board 30 to protect the sensitivecomponents and contacts on the circuit board 30. The spacing layer 34may be separate from or integrated with the circuit board 30.

[0061] In addition, one or more alignment holes 36 are preferablyprovided through each of the layers 30, 32, and 34 and partially throughthe upper portion 12A and the lower portion 12B of the base plate. Aguide pin (not shown) is preferably placed in each of the alignmentholes, which ensures a preferably unique orientation of the layers 30,32, and 34 with the portions of the base plate 12A, 12B as they arejoined together.

[0062] One or more screw holes 38 are provided through the bottomportion 12B of the base plate, each of the layers 30, 32, 34, andpartially through the upper portion 12A of the base plate to accommodatea screw, which joins the portions of the base plate together andsandwiches the layers. The screw maintains compression between theportions of the base plate, which aids in preventing leakage of fluidfrom the channel. FIG. 5b shows an alternative embodiment of the baseplate 12 shown in FIG. 5a, in which the screw hole 38 has been relocatednearer an external surface of the base plate.

[0063]FIG. 6a shows the circuit board 30 with eight (8) sensors 18. Eachof the sensors 18 is preferably positioned within a depression on thecircuit board 30 and affixed to the circuit board 30 by an adhesive,surface mount technology (SMD), wire bond technology, flip-chiptechnology, or the like. The sensor 18 is preferably connected to bondpads 40, which are coupled to electrically conductive traces 42 on thecircuit board 30. The traces 42 are brought to the edge of the board,which is preferably accessible from the outside of the base plate 12when the upper portion 12A and the lower portion 12B of the base plate12 are joined together.

[0064] The sensors 18 are advantageously encapsulated within andelectrically accessible outside the integrated fluid sensing deviceformed in accordance with the present invention. Thus, the fragilecomponents of the sensor 18 are inherently protected from shock,humidity, dust, corrosive chemicals, and other environmental hazards.

[0065]FIG. 6b is a side, cross-sectional view of the circuit board 30taken along the line B-B′, which shows the alignment holes 36, screwhole 38 and sensor 18. FIG. 6c shows an alternative embodiment of thecircuit board 30 shown in FIG. 6a, which includes a microprocessor, amicrocontroller, or an application-specific integrated circuit (ASIC)44. The ASIC 44 monitors and processes signals from each of the sensors18 and outputs the processed information externally to the base plate12. The ASIC 44 may include circuitry that enables it to interface toFieldbus compatible components and controllers.

[0066] Fieldbus is a commercial standard describing a digital, serial,multi-drop, two-way communication link, which interconnects measurementand control equipment such as sensors, actuators, and controllers. Itserves as a Local Area Network (LAN) for instruments used in processcontrol and manufacturing automation applications and has a built-incapability to distribute the control application across the network.

[0067]FIG. 6d shows an alternative embodiment of the circuit board 30shown in FIG. 6C, in which, in addition to the ASIC 44, a telemetricunit 46 is provided for the wireless transmission of informationprocessed by the ASIC 44. The telemetric unit 46 preferably inputs asignal from each of the sensors 18, which is representative of thesensed physical characteristic and outputs a wireless signal, such as aradio frequency or infrared signal.

[0068]FIG. 7a shows a top view of the spacing layer 34, which is alsoshown in FIGS. 5a and 5 b. The spacing layer 34 is preferably used toprotect the sensitive components of the sensor 18 and the bond pads 40,which electrically connect the sensor 18 to the edge of the circuitboard 30. The spacing layer 34 is preferably sealed by an appropriatechoice of pliable material deposited on the spacing layer 34 or byinserting an additional sealing layer between the spacing layer 34 andthe circuit board 30. Bumps and/or recesses may be integrated onto thespacing layer 34 to further protect corresponding sensors 18 and bondpads 40 on the circuit board 30. The bumps or recesses may alternativelybe incorporated on the circuit board 30 without requiring a separatespacing layer 34. FIG. 7b is a side, cross-sectional view of the spacinglayer 34 taken along line C-C′, which shows the alignment holes 36, thescrew hole 38, and an aperture 48 for the sensor 18.

[0069]FIG. 8a shows the sealing layer 32, which prevents leakage fromthe channel to the exterior of the base plate 12. The functionality ofthe sealing layer 32 could alternatively be incorporated into thecircuit board 30 by applying, for instance, independent seals aroundeach of the orifices in the circuit board 30. FIG. 8b is a side,cross-sectional view of the sealing layer 32 taken across the line D-D′,which shows the alignment holes 36, the screw hole 38, and the aperture38 for the sensor 18.

[0070]FIG. 9 shows the integrated fluid flow device formed in accordancewith the present invention. The circuit board 30, which includes one ormore sensors 18 is sandwiched between the upper portion 12A and thelower portion 12B of the base plate. The primary flow of fluid withinthe channel is indicated by arrow L, which is preferably diverted aroundthe sensor 18 through the bypass path L′. A small portion L″ of theprimary flow L flows through the sensor 18 and continues through thechannel into the upper portion 12A of the base plate. Once the fluidexits the upper portion 12A, it is preferably outputted to pneumaticcomponents, such as pneumatically actuated cylinders or valves.

[0071] It is anticipated that the integrated fluid sensing device of thepresent invention can be implemented with any quantity of valves ormanifolds used to control hydraulic and/or pneumatic equipment. It isalso anticipated that the sensor can measure any conceivable physicalcharacteristic of the fluid, such as temperature, flow rate, pressure,and the like. It is further anticipated that the sensor can beimplemented as alternative types of transducers, such as a magneticflowmeter, hot-wire anemometer, bimetallic strip, thermocouple, pressurecell, or pressure transducer. Additional details concerning transducerscan be found in S. Wolf, “Guide to Electronic Measurements andLaboratory Practice”, Prentice-Hall, Inc., pp. 414-451, (1973), which isincorporated herein by reference.

[0072] The hot-wire anemometer 19 is shown in FIG. 2d and includes afine resistive wire 21, which is heated by a current passing through it.If a cooler fluid flows past the wire 21, the fluid removes heat fromthe wire 21. The rate of heat transfer varies with the type of fluid,but it also tends to vary as the square root of the velocity at whichthe fluid flows past the wire 21. If the current in the wire 21 is keptconstant, the change in resistance due to the cooling will yield avoltage signal, which can be monitored to indicate flow rate. Since thediameter of the wire 21 can be made very small, the anemometer 19 can bemade very sensitive and responsive to high-frequency changes in the flowrate.

[0073] A flow sensor 50 formed in accordance with the present invention,which is used to measure the flow of fluid is shown in FIG. 10. Thepaddle 54 is preferably mechanically coupled to that portion 58 of theflow sensor 50 surrounding an aperture or orifice 52 by a bender orsupport member 56. The support member 56 preferably positions the paddle54 in the orifice 52 and includes an implanted piezo-resistive fullWheatstone bridge 70.

[0074] The overall length and width of the flow sensor in the preferredembodiment, as indicated by dimension B, is approximately 5 mm. The flowsensor 50 preferably includes a paddle 54 at least partially disposed inthe orifice 52. The length and width of the orifice 52 of the preferredembodiment, as indicated by dimension A, is approximately 1 mm. Thewidth of the support member 56 in the preferred embodiment is preferablyabout 100 μm, as indicated by dimension D in FIG. 12, which shows amagnified view of an actual layout of the support member 56. Each of thedimensions in the preferred embodiment of the flow sensor may beadjusted based upon design choice and/or sensor specifications whileremaining within the scope of the present invention.

[0075] The surface area of the support member 56 is preferably less thanthat of the paddle 54 to concentrate the mechanical stress of deflectionon the support member 56, and thus increase the sensitivity of the flowsensor 50. The overall size of the flow sensor 50 is preferablydetermined by the surface area of the paddle 54, which is adjustable inaccordance with the needs and or sensitivity required for the specificcontrol task.

[0076] The fluid to be measured is preferably directed through theorifice 52 in the flow sensor 50. The dynamic pressure provided by thefluid preferably deflects the paddle 54, which places mechanical stresson the support member 56. As shown in FIG. 11, the mechanical stress onthe support member 56 changes the resistance of piezo-resistive stressgauges 72, 74, 76, and 78 coupled by ohmic contacts or conductors 62,64, 66, and 68 in a Wheatstone bridge 70 disposed on the support member56.

[0077] This change in resistance creates a corresponding change involtage, which is preferably provided on one or more electrical contactsor doped regions 60 coupled to the conductors 62, 64, 66, and 68, whichare shown in greater detail in the exploded view of the support member56 in FIG. 11. The strain gauges 72 and 76 are preferably subjected totransverse stress in response to deflection of the paddle 54. The straingauges 74 and 78 are preferably subjected to longitudinal stress inresponse to deflection of the paddle 54.

[0078] The output voltage of the Wheatstone bridge 70 is preferablyproportional to the square of the volumetric flow rate. The sensitivityof the flow sensor 50 depends on the size of the orifice 52 and the sizeor surface area of the paddle 54, both of which are adjustable over abroad range. Thus, since the paddle 54 is preferably perpendicularlyoriented to the direction of fluid flow, which is indicated by arrow Cin FIGS. 10 and 11, as fluid passes through the orifice, the kineticpressure of the fluid induces a mechanical stress on the support member56. This mechanical stress is preferably detected by the piezo-resistivestress gauges or resistors 72, 74, 76, and 78 in the Wheatstone bridge70.

[0079] The stress gauges 72, 74, 76, and 78 are preferably exclusivelydisposed on the support member 56. The paddle 54 is preferably usedexclusively for its mechanical resistance to fluid flow without anypassive or active electronic components disposed thereon. Thus, the flowsensor 50 formed in accordance with a preferred embodiment of thepresent invention is preferably a two-part flow sensor including astandardized support member 56, which can be generically used for allsuch flow sensors, and a customizable paddle 54, which may bedimensionally tailored to the sensitivity requirements of a specificapplication without substantially changing the overall manufacturingprocess of the flow sensor 50.

[0080] Further, since the flow sensor 50 formed in accordance with thepresent invention preferably includes a full Wheatstone bridge toachieve optimal signal output and sensitivity, both positive andnegative deflections must be detected by the strain gauges 72, 74, 76,and 78. Wire or foil strain gauges merely exhibit sensitivity tolongitudinal stress, and thus must be disposed on both the front andrear faces of the stressed component to detect the positive and negativedeflections required by the full Wheatstone bridge. However, use ofpiezo-resistive stress gauges 72, 74, 76, and 78 in the flow sensor 50formed in accordance with the present invention, which are able todetect both longitudinal and transverse stress, enable the fullWheatstone bridge 70 to be disposed on only one side of the supportmember 56, which significantly simplifies and reduces the cost ofmanufacturing the flow sensor 50 in accordance with the presentinvention.

[0081] From the foregoing description, it will be appreciated that theintegrated fluid sensing device formed in accordance with the presentinvention significantly reduces measurement errors, space requirements,external tubing, connectors, fittings, and the cost of installation andmaintenance of sensors that measure the physical characteristics of afluid used to control hydraulic or pneumatic equipment. It will also beappreciated that the integrated fluid sensing device of the presentinvention enables sensors to be mounted on a single circuit board havingcommon signal processing, communication, error control, and connectivecircuitry.

[0082] Further, it will be appreciated that the integrated fluid sensingdevice formed in accordance with the present invention is able toreadily display and transmit data, which represents physicalcharacteristics of the fluid used to control hydraulic and pneumaticequipment. It will also be appreciated that the integrated fluid sensingdevice formed in accordance with the present invention substantiallyencloses sensors that measure the physical characteristics of the fluidand protects these sensors from environmental hazards.

[0083] It will also be appreciated that the flow sensor formed inaccordance with the present invention can readily be adapted todifferent flow rates without substantial change or additional cost inthe manufacturing process. It will also be appreciated that the flowsensor includes a generic or standardized support member having one ormore strain gauges disposed on only one side of the support member and acustomizable paddle displaced by fluid flow, which does not include astrain gauge.

[0084] Although illustrative embodiments of the present invention havebeen described herein with reference to the accompanying drawings, it isto be understood that the invention is not limited to those preciseembodiments, and that various other changes and modifications may beeffected therein by one skilled in the art without departing from thescope or spirit of the invention.

What is claimed is:
 1. A flow sensor comprising: a paddle being disposedat least partially in an orifice, a fluid flow directed through theorifice, the paddle being displaced in response to the fluid flow; and asupport member positioning the paddle at least partially in the orifice,the support member including a plurality of strain gauges, the pluralityof strain gauges being disposed on only one side of the support member,at least one of the plurality of strain gauges being mechanicallystressed in response to the paddle being displaced by the fluid flow. 2.A flow sensor as defined by claim 1, wherein the paddle includes asurface area, the surface area of the paddle being adaptable to providedifferent displacements of the paddle in response to the fluid flow. 3.A flow sensor as defined by claim 1, wherein the paddle includes a firstsurface area, the support member including a second surface area, thefirst surface area being unequal to the second surface area.
 4. A flowsensor as defined by claim 1, wherein the paddle does not have anyelectrical components mounted thereon.
 5. A flow sensor as defined byclaim 1, wherein the plurality of strain gauges is operativelyconfigured in a Wheatstone bridge.
 6. A flow sensor as defined by claim1, wherein at least one of the plurality of strain gauges is responsiveto at least one of transverse stress and longitudinal stress.
 7. A flowsensor as defined by claim 1, wherein at least one of the plurality ofstrain gauges is piezo-resistive.
 8. A method of sensing flow, themethod comprising the steps of: disposing a paddle at least partially inan orifice; directing a fluid flow through the orifice, the paddle beingdisplaced in response to the fluid flow; positioning the paddle at leastpartially in the orifice by a support member, the support memberincluding a plurality of strain gauges; and disposing the plurality ofstrain gauges on only one side of the support member, the plurality ofstrain gauges being mechanically stressed in response to the paddlebeing displaced by the fluid flow.
 9. A method of sensing flow asdefined by claim 8, further comprising the step of adapting a surfacearea of the paddle to provide different displacements of the paddle inresponse to the fluid flow.
 10. A method of sensing flow as defined byclaim 8, further comprising the step of providing a first surface areaof the paddle unequal to a second surface area of the support member.11. A method of sensing flow as defined by claim 8, further comprisingthe step of disposing the plurality of strain gauges exclusively on thesupport member.
 12. A method of sensing flow as defined by claim 8,further comprising the step of configuring the plurality of straingauges operatively in a Wheatstone bridge.
 13. A method of sensing flowas defined by claim 8, further comprising the step of providing at leastone of the plurality of strain gauges as responsive to at least one oftransverse stress and longitudinal stress.
 14. A method of sensing flowas defined by claim 8, further comprising the step of providing at leastone of the plurality of strain gauges as a piezo-resistive strain gauge.15. A fluid sensing device, the fluid sensing device comprising: a fluidflow device including a first mating portion and a second matingportion, the first mating portion including a first aperture, the secondmating portion including a second aperture, the first aperture and thesecond aperture being at least partially aligned such that the firstaperture and the second aperture define a channel through the first andsecond mating portions when the first and second mating portions arejoined together, the channel being able to communicate fluidtherethrough; and a circuit board sandwiched between the first matingportion and the second mating portion, the circuit board including atleast one flow sensor, the at least one flow sensor being at leastpartially aligned with the channel, the at least one flow sensor beingable to detect a physical characteristic of the fluid flowing throughthe channel, the flow sensor including a paddle and a support member,the paddle being at least partially disposed in the channel, the paddlebeing displaced in response to fluid flowing through the channel, thesupport member positioning the paddle at least partially in the channel,the support member including a plurality of strain gauges, the pluralityof strain gauges being mechanically stressed in response to the paddlebeing displaced.
 16. A fluid sensing device as defined by claim 15,wherein the plurality of strain gauges are disposed on only one side ofthe support member.
 17. A fluid sensing device as defined by claim 15,wherein the fluid flow device includes a valve manifold and a baseplate, the base plate being removably coupled to the valve manifold, thebase plate including the first mating portion and the second matingportion.
 18. A fluid sensing device as defined by claim 15, wherein thefirst mating portion includes a plurality of first apertures and thesecond mating portion includes a plurality of second apertures, theplurality of first apertures and the plurality of second apertures beingat least partially aligned such that the plurality of first aperturesand the plurality of second apertures define a plurality of channelsthrough the first and second mating portions when the first and secondmating portions are joined together, the plurality of channels beingable to communicate fluid therethrough, the circuit board including aplurality of flow sensors, the plurality of flow sensors being at leastpartially aligned with the plurality of channels, the plurality of flowsensors being able to detect a physical characteristic of the fluidflowing through the plurality of channels.
 19. A fluid sensing device asdefined by claim 15, wherein the paddle includes a surface area, thesurface area of the paddle being adaptable to provide differentdisplacements of the paddle in response to the fluid flow.
 20. A fluidsensing device as defined by claim 15, wherein the paddle includes afirst surface area, the support member including a second surface area,the first surface area being unequal to the second surface area.
 21. Afluid sensing device as defined by claim 15, wherein the paddle does nothave any electrical components mounted thereon.
 22. A fluid sensingdevice as defined by claim 15, wherein the plurality of strain gauges isoperatively configured in a Wheatstone bridge.
 23. A fluid sensingdevice as defined by claim 15, wherein at least one of the plurality ofstrain gauges is responsive to at least one of transverse stress andlongitudinal stress.
 24. A fluid sensing device as defined by claim 15,wherein at least one of the plurality of strain gauges ispiezo-resistive.
 25. A fluid sensing device comprising: at least onevalve; a base plate removably coupled to the at least one valve, thebase plate including a first portion and a second portion, the firstportion including a first mating surface, the second portion including asecond mating surface the base plate including a channel through thefirst and second portions when the first and second mating surfaces arejoined together, the channel being in fluid communication with the atleast one value; and a circuit board sandwiched between the firstportion and the second portion, the circuit board including at least oneflow sensor, the at least one flow sensor being at least partiallyaligned with the channel, the at least one flow sensor being able todetect a physical characteristic of the fluid flowing through thechannel, the at least one flow sensor including a paddle and a supportmember, the paddle being at least partially disposed in the channel, afluid flow being directed through the channel, the paddle beingdisplaced in response to the fluid flow, the support member positioningthe paddle at least partially in the channel, the support memberincluding a plurality of strain gauges the plurality of strain gaugesbeing mechanically stressed in response to the paddle being displaced bythe fluid flow.
 26. A fluid sensing device as defined by claim 25,wherein the plurality of strain gauges are disposed on only one side ofthe support member.
 27. A fluid sensing device as defined by claim 25,wherein the base plate includes a plurality of channels through thefirst and second portions when the first and second mating surfaces arejoined together, the plurality of channels being able to communicatefluid therethrough, the circuit board including a plurality of flowsensors, the plurality of flow sensors being at least partially alignedwith the plurality of channels, the plurality of flow sensors being ableto detect a physical characteristic of the fluid flowing through theplurality of channels.
 28. A fluid sensing device as defined by claim25, wherein the paddle includes a surface area, the surface area of thepaddle being adaptable to provide different displacements of the paddlein response to the fluid flow.
 29. A fluid sensing device as defined byclaim 25, wherein the paddle includes a first surface area, the supportmember including a second surface area, the first surface area beingunequal to the second surface area.
 30. A fluid sensing device asdefined by claim 25, wherein the paddle does not have any electricalcomponents mounted thereon.
 31. A fluid sensing device as defined byclaim 25, wherein the plurality of strain gauges is operativelyconfigured in a Wheatstone bridge.
 32. A fluid sensing device as definedby claim 25, wherein at least one of the plurality of strain gauges isresponsive to at least one of transverse stress and longitudinal stress.33. A fluid sensing device comprising: at least one valve including atleast one duct and a substantially flat first mating surface; a baseplate removably coupled to the at least one valve, the base plate havinga second mating surface, the base plate including at least one channelin fluid communication with the at least one duct; and a circuit boardsandwiched between the first mating surface of the valve and the secondmating surface of the base plate, the circuit board comprising at leastone flow sensor, the at least one flow sensor being at least partiallyaligned with at least one of the duct and the channel, the at least oneflow sensor being able to detect a physical characteristic of a fluidflowing therethrough, the at least one flow sensor including a paddleand a support member, the paddle being at least partially aligned withat least one of the duct and the channel, a fluid flow being directedthrough the channel, the paddle being displaced in response to the fluidflow, the support member positioning the paddle, the support memberincluding a plurality of strain gauges, the plurality of strain gaugesbeing mechanically stressed in response to the paddle being displaced bythe fluid flow.
 34. A fluid sensing device as defined by claim 33,wherein the plurality of strain gauges is disposed on only one side ofthe support member.
 35. A fluid sensing device as defined by claim 33,wherein the at least one valve includes a plurality of ducts, the baseplate including a plurality of channels in fluid communication with theplurality of ducts, the circuit board comprising a plurality of flowsensors at least partially aligned with the plurality of ducts and theplurality of channels.
 36. A fluid sensing device as defined by claim33, wherein the paddle includes a surface area, the surface area of thepaddle being adaptable to provide different displacements of the paddlein response to the fluid flow.
 37. A fluid sensing device as defined byclaim 33, wherein the paddle includes a first surface area, the supportmember including a second surface area, the first surface area beingunequal to the second surface area.
 38. A fluid sensing device asdefined by claim 33, wherein the paddle does not have any electricalcomponents mounted thereon.
 39. A fluid sensing device as defined byclaim 33, wherein the plurality of strain gauges is operativelyconfigured in a Wheatstone bridge.
 40. A fluid sensing device as definedby claim 33, wherein at least one of the plurality of strain gauges isresponsive to at least one of transverse stress and longitudinal stress.